Activist Is Intensifying Campaigning and Threatening a Fight Over the Volcano Board

Engaged Capital LLC urged Volcano Corp. to find itself a buyer or a new chief executive, according to a letter Engaged released Monday, a change in the activist's approach at the medical-device company after the stock has halved this year.

Engaged, which owns about 5.1% of Volcano, has spent more than a year talking to the company, in what it had said were constructive talks, pushing a share buyback and changes to management...